I located the bug. When you use the shell commands compress to/compress with options you have indeed 0 files in archive/testing.
When you use the ‘PA dashboard’ then 3 files are reported in ‘files in archive’/test report.
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Testing archive: testreport.pa – 27/07/2017 14:05
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Files in archive: 3
File size: 621,545 bytes

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Done. – 27/07/2017 14:05
There were no errors in the archive: testreport.pa